Wafer processing apparatus with a processing vessel, upper and lower separately sealed heating vessels, and means for maintaining the vessels at predetermined pressures

ABSTRACT

A thermal processing apparatus for a semi-conductor wafer. A holder is provided within a processing vessel on which the wafer to be processed is placed. Upper and lower heaters are provided above and below the holder in order to heat the wafer. Each of the heaters are attached within heating vessels. A gas supply head supplies a processing gas in a shower form between the upper heater and the holder. The uniformity of the surface temperature of the wafer is improved by heating the wafer from both above and below.

TECHNICAL FIELD

The present invention relates to a single-wafer type of thermalprocessing apparatus for subjecting a semiconductor wafer or the like toa thermal process such as film-formation, oxidation, or thermaldiffusion.

BACKGROUND ART

During the fabrication of a semiconductor integrated circuit, thermalprocessing steps for performing film-formation, oxidation, or diffusionon a surface of a semiconductor wafer and pattern-etching steps aregenerally repeated. When wafers of, for example, an 8-inch size are tobe subjected to thermal processing, a vertical batch type of thermalprocessing apparatus is mainly used in the art because it is capable ofsubjecting a large number of wafers to thermal processing at the sametime. An important point with this type of thermal processing is goodcontrol over the uniformity of temperature within the wafer surface,from the viewpoint of improving uniformity of the characteristics of thecompleted circuits, and hence the yield thereof.

Concomitant with the increasing integration and decreasing size ofcircuits, the wafer size is also increasing, so that the use of waferssuch as those of 12 inches in size is being investigated.

If such wafers increase in size from 8 inches to 12 inches(approximately 30 cm), the self-weight of each wafer is multiplied toapproximately 2.5 to 3 times that of an 8-inch wafer, and moreoverconsiderations of thermal uniformity within the wafer surface make itdifficult for a prior-art batch type of vertical thermal processingapparatus to cope therewith. In other words, one result of themultiplication of the self-weight of the wafer as described above isthat a wafer boat for holding a large number of wafers cannot cope fromthe strength point of view; alternatively, because the surface area ofthe wafer has increased due to the increase in diameter, a method thatrelies on heating from the sides of wafers that are arrayed at apredetermined pitch will find it difficult to heat the wafer surfacesuniformly.

To solve the above problems, there have been various proposals for asingle-wafer type of thermal processing apparatus for processing onewafer at a time, wherein a wafer that is supported or mounted on a waferholder is heated by a halogen lamp or resistance heater of theapparatus, disposed below the wafer holder. However, if such a prior-artsingle-wafer type of thermal processing apparatus is used to heat alarger-diameter wafer, it is fairly difficult to achieve good uniformityof the surface temperature of the wafer, with the amount of heatgenerated per unit surface area by a heater of a current type, and itcan not be said that a conventional apparatus is sufficient therefor.

The present invention was devised in order to solve the above problems.A main objective of the present invention is to provide a single-wafertype of thermal processing apparatus that is capable of improving theuniformity of temperature within the surface of an object to beprocessed, such as a wafer.

DISCLOSURE OF INVENTION

In order to achieve the above objective, the present invention providesa thermal processing apparatus having a processing vessel and a holderfor an object to be processed, which is provided within the processingvessel to hold an object to be processed, wherein the thermal processingapparatus comprises: a lower heating means provided within theprocessing vessel and below the holder, for heating the object to beprocessed; an upper heating means provided within the processing vesseland above the holder for an object, for heating the object; and aprocessing gas supply means for supplying a processing gas to an areabetween the holder and the upper heating means.

By disposing heating means above and below the holder and by alsoproviding a gas supply portion between the holder for an object to beprocessed and the upper heating means in this manner, the object to beprocessed can be heated from both surfaces thereof so that the heatingof the object to be processed can be achieved with good control, bothuniformly and at a high level of energy; it is possible to supply theprocessing gas directly to the object to be processed; and it is alsopossible to prevent the formation of unwanted films on components suchas the processing vessel and increase the uniformity of the processingperformed on the object to be processed.

It is thus possible to provide a predetermined gas supply system and gasexhaust system within each of the heating means vessels for the upperand lower heating means that are isolated in an airtight manner from theprocessing vessel. In such a case, the pressure differences between theinterior of the processing vessel and the interiors of the heating meansvessels can be made extremely small; the partitioning walls between theheating means vessels and the processing vessel can be thinned by aconsequent amount to a degree at which they can cope with such pressuredifferences; and thus the thermal efficiency of each heating means canbe increased, the uniformity of surface temperature can be improved, andthe controllability of heating can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall view of a processing system comprising asingle-wafer thermal processing apparatus in accordance with thisinvention;

FIG. 2 is a sectional view through a first embodiment of thesingle-wafer thermal processing apparatus within the processing systemof FIG. 1;

FIG. 3 is a plan view of the heating means provided in the thermalprocessing apparatus of FIG. 2;

FIG. 4 is a perspective view of a uniform-heating ring member;

FIG. 5 is a schematic view of a gas supply system and a gas exhaustsystem;

FIGS. 6A and 6B are graphs of pressure changes within the processingvessel and heating means vessel of the prior art and the presentinvention, respectively;

FIGS. 7A and 7B are graphs of the temperature profiles within thesurface of the object to be processed, for the single-surface heating ofthe prior art and the double-surface heating of this invention;

FIGS. 8A and 8B show different variants of the uniform-heating ringmember;

FIG. 9 is a vertical sectional view through a variant of the thermalprocessing apparatus in which the internal structural members areintegrated;

FIG. 10 is a horizontal sectional view through the integrated internalstructural members of FIG. 9;

FIG. 11 is a perspective schematic view of the integrated internalstructural members of FIG. 9;

FIG. 12 shows a variant of the gas supply system and gas exhaust system;

FIG. 13 is a vertical sectional view through a second embodiment of thesingle-wafer thermal processing apparatus of the present invention;

FIG. 14 is a perspective view of the holder for an object to beprocessed used in the thermal processing apparatus of FIG. 13;

FIG. 15 is a view of the resistance heating means used in the thermalprocessing apparatus of FIG. 13;

FIG. 16 is a vertical sectional view through a third embodiment of thesingle-wafer thermal processing apparatus of the present invention;

FIG. 17 is a perspective view of the holder for an object to beprocessed used in the thermal processing apparatus of FIG. 16;

FIG. 18 is a vertical sectional view through a variant of the holder foran object to be processed;

FIG. 19 is a partially cutaway perspective view of the holder for anobject to be processed of FIG. 18;

FIG. 20 is a view of a variant of the holder for an object to beprocessed;

FIG. 21 is an illustrative view of the operations when an object to beprocessed is conveyed into and out of the holder;

FIG. 22 is a vertical sectional view of an embodiment of the thermalprocessing apparatus using a supplementary support stand;

FIG. 23 is a perspective view of the supplementary support stand of FIG.22;

FIG. 24 shows a variant of the supplementary support stand;

FIG. 25 is a partially cutaway view of the supplementary support standof FIG. 24;

FIG. 26 is a vertical sectional view of another variant of thesupplementary support stand; and

FIG. 27 is a schematic structural view of an example provided with apre-heating chamber between the processing vessel and the load-lockchamber.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the thermal processing apparatus in accordance with thepresent invention will be described below, with reference to theaccompanying drawings.

A processing system that uses the thermal processing apparatus of thepresent invention is shown schematically in FIG. 1. In addition to athermal processing apparatus 2 in accordance with this invention, whichessentially subjects an object to be processed (a semiconductor wafer)to thermal processing, a thermal processing system 3 shown in thisfigure is mainly configured of a load-lock chamber 42 provided in avacuum-sealable manner at a previous stage of the thermal processingapparatus 2, with a gate valve G1 therebetween, and a cassette chamber 5provided at a previous stage of the load-lock chamber 42, with a gatevalve G2 therebetween.

Within this cassette chamber 5 is provided an elevatable cassette stand7 with a cassette 9 containing a plurality of wafers W, such as 5 to 35wafers, mounted thereupon. The load-lock chamber 42 is connected to avacuum exhaust system 11 with a vacuum pump (not shown in the figure)therebetween so that the interior thereof can be evacuated. A robothaving an extendable and rotatable conveyor arm 44 is provided in theinterior of the load-lock chamber 42 in such a manner that the wafers Wcan be transferred to and from the thermal processing apparatus 2 andthe cassette chamber 5 thereby. Note that a supply system (not shown inthe figure) for an inert purging gas such as N₂ is also provided in theload-lock chamber 42.

The thermal processing apparatus 2 has a processing vessel 4 that isformed to a cylindrical shape of a material such as aluminum, andapertures are formed in each of a base portion and a ceiling portion ofthe processing vessel 4, as shown in FIG. 2. A lower heating meansvessel 6 made of a material such as quartz is provided in a hermeticallysealed state within the aperture of the base portion and an upperheating means vessel 8 made of the same quartz is provided in a sealedstate within the aperture of the ceiling portion, such that each isseparated hermetically from the interior of the processing vessel 4.

This lower heating means vessel 6 is configured of a thin dome-shapedportion 6A, which is inserted in a convex form towards the interior ofthe processing vessel 4 and has a flat upper edge, and a thick-plate lidportion 6B, which is provided to cover a lower aperture thereof and hasan outer side exposed to the atmosphere, with the lower heating meansvessel 6 being provided in an airtight manner in the base portion of theprocessing vessel 4 with a sealing member 10 such as an O-ringtherebetween.

The thickness of the thin dome-shaped portion 6A is set to be as thin asapproximately 4 mm, for example, which suppresses thermal losses in thisportion and also gives a favorable thermal response characteristic.Since the thickness of this dome-shaped portion 6A is made thin in thismanner, this allows the pressure within this lower heating means vessel6 to vary to follow pressure variations within the processing vessel 4,as will be described later, and the pressure difference within the twovessels can be set in such a manner that it is less than the pressureresistance of the dome-shaped portion 6A. The thickness of thethick-plate lid portion 6B is set to a thickness that providesresistance to atmospheric pressure, such as approximately 15 to 20 mm.

A support shaft 15 of a holder 14 for an object to be processed, made ofa material such as quartz, is passed in an airtight manner verticallythrough a central portion of the lower heating means vessel 6 with amagnetic fluid seal 12 therebetween, so as to be provided rotatablytherein in order to heat the wafer uniformly, three claw portions 14Aare formed in the upper edge of the holder 14 to be disposedequidistantly on the same periphery thereof, and the configuration issuch that a peripheral portion of the rear surface of a semiconductorwafer W which is the object to be processed is supported on the clawportions 14A.

In this case, the dome-shaped portion 6A intrudes in a convex mannerinto the processing vessel 4, as described above, and is formed to be asclose as possible to the rear surface of the semiconductor wafer W,means such as a resistance heater 16 is provided over substantially theentire surface of the inner side of an upper edge flat surface portionof this dome-shaped portion 6A as a lower heating means, with theconfiguration being such that the wafer W is heated from the lowersurface thereof. A rotational drive mechanism 22 like a motor, forexample, is provided on a lower portion of the support shaft 15 of theholder 14, with the configuration being such that the wafer W is heatedwhile rotating.

A purge gas introduction port 18 for introducing a purge gas such as N₂into the lower heating means vessel 6 and a purge gas exhaust port 20for exhausting the internal environmental gas therefrom are eachprovided in the thick-plate lid portion 6B.

In a similar manner to the lower heating means vessel 6, the upperheating means vessel 8 is configured of a thin bowl-shaped portion 8A,which is inserted in a convex form towards the interior of theprocessing vessel 4 and has a flat lower edge, and a thick-plate lidportion 8B, which is provided to cover a upper aperture thereof and hasan outer side exposed to the atmosphere, with the upper heating meansvessel 8 being provided in an airtight manner in the ceiling portion ofthe processing vessel 4 with a sealing member 24 such as an O-ringtherebetween.

The thickness of the bowl-shaped portion 8A is set to be as thin asapproximately 4 mm, for example, which suppresses thermal losses in thisportion and also gives a favorable thermal response characteristic.

Since the thickness of this bowl-shaped portion 8A is made thin in thismanner, this allows the pressure within this upper heating means vessel8 to vary to follow pressure variations within the processing vessel 4,and the pressure difference within the two vessels can be set in such amanner that it is less than the pressure resistance of the bowl-shapedportion 8A. The thickness of the thick-plate lid portion 8B is set to athickness that provides resistance to atmospheric pressure, such asapproximately 15 to 20 mm.

Means such as a resistance heater 26 is provided over substantially theentire surface of the inner side of a lower edge flat surface portion ofthis bowl-shaped portion 8A as an upper heating means, with theconfiguration being such that the wafer W is heated from the uppersurface thereof. In this case, the distance between each of the upperand lower resistance heaters 26 and 16 from the wafer W is set to beextremely small, such as on the order of 10 mm, so that the wafer W isheated efficiently from above and below.

A gas supply head 28 that has a vessel-shaped shower-head structure andis made of a material such as quartz is provided on a lower surface sideof the upper heating means vessel 8, and a processing gas introductionpipeline 30 for introducing a processing gas is connected thereto. Theconfiguration is such that the processing gas introduced by thisintroduction pipeline 30 is ejected from a large number of ejectionholes 32 provided over the entire lower surface of the gas supply head28 towards the entire region of the upper surface of the wafer W.

A purge gas introduction port 36 for introducing a purge gas such as N₂into the upper heating means vessel 8 and a purge gas exhaust port 38for exhausting the internal environmental gas therefrom are eachprovided in the thick-plate lid portion 8B.

A gas exhaust port 34 connected to a vacuum pump (not shown in thefigure) for exhausting the environment within the processing vessel 4 isprovided in a peripheral edge portion of the base portion thereof, and apurge gas introduction port 40 for introducing a purge gas such as N₂into the processing vessel 4 is provided in the ceiling portion thereof.Note that the gas supply head 28 could also be used as the purge gasintroduction port 40.

The gate valve G1 that is opened and closed when a wafer W is conveyedin or out is provided in a side wall of the processing vessel 4, theload-lock chamber 42 is provided via the gate valve G1, and the base ofthe conveyor arm 44 therewithin is supported on an elevatable slidingmechanism 46 so that the entire arm 44 can be raised and loweredthereby.

Each of the upper and lower heaters 26 and 16 is divided into aplurality of concentric circular zones, such as three zones 26a (16a),26b (16b), and 26c (16c), as shown in FIG. 3, with the configurationbeing such that power supplied from an electrical power supply source 48is controlled individually for each of the zones so that power can besupplied separately thereto. Note that the number of zones is notlimited to three; it could equally well be two or four or more.

As shown in FIG. 2, a uniform-heating ring member 50 made of a materialsuch as quartz is provided on a peripheral edge portion of the holder 14for the object to be processed within the processing vessel 4 in such amanner as to cover a side portion of the wafer W supported thereon (seealso FIG. 4), with the configuration being such that the wafer W isheated by radiant heat reflected therefrom and, at the same time, athermal insulation function is exhibited with respect to the side wallsof the processing vessel 4. A circular-arc-shaped portion correspondingto the gate valve G1 on one side of this uniform-heating ring member 50is cut out and separated from the main unit side thereof as a shutterportion 50A, and a shutter rod 52 provided penetrating through the baseportion of the processing vessel 4 is connected to this shutter portion50A. An expandable metal bellows 54 that permits vertical movement whilemaintaining an airtight seal is provided on the penetrating portion ofthis shutter rod 52, whereby this shutter portion 50A is enabled to movevertically by an elevator mechanism 53 when the wafer is conveyed in orout. This shutter portion 50A is moved vertically in synchronizationwith the opening and closing of the gate valve G1.

The gas supply system and gas exhaust system within the processingvessel 4 for controlling the pressures within the lower and upperheating means vessels 6 and 8 are configured as shown in FIG. 5. Inother words, a gas supply system 56 for supplying a purge gas such as N₂has a common gas passageway 58 for connection in common to the purge gasintroduction ports 40, 18, and 36, and this is connected to the purgegas introduction ports 40, 18, and 36 by branch pipelines 60 that branchtherefrom. A supply-side fixed needle valve 62 that opens at apredetermined pressure between upstream and downstream sides thereof isinserted into each of these branch pipelines 60, with the configurationbeing such that an N₂ supply is provided therethrough without any largedifference in pressures being created between the vessels when N₂ issupplied to return the pressure to atmospheric pressure, for example.

In addition, a gas exhaust system 64 for exhausting environmental gaswithin the vessels has a common gas passageway 66 for connection incommon to the gas exhaust port 34 of the processing vessel 4 and thepurge gas exhaust ports 20 and 38 of the lower and upper heating meansvessels 6 and 8, and this is connected to the gas exhaust port 34 andthe purge gas exhaust ports 20 and 38 by branch pipelines 68 that branchtherefrom. An exhaust-side fixed needle valve 70 that opens at apredetermined pressure between upstream and downstream sides thereof isinserted into each of these branch pipelines 68, with the configurationbeing such that environmental gas is exhausted therethrough without anylarge difference in pressures being created between the processingvessel and the other vessels when the processing vessel is evacuated,for example.

A mass-flow controller 72 and a vacuum pump 74 are also inserted in thecommon gas passageway 66 for exhaust, to ensure that fixed amounts ofgas are exhausted at a time during the exhaust process.

The operation of the thus configured embodiment of the present inventionwill now be described.

First of all, a wafer W held by the conveyor arm 44 of the load-lockchamber 42 is conveyed into the processing vessel 4 through the openedgate valve G1 by extending the arm 44, then the arm 44 is loweredthrough a very small distance to transfer the wafer W onto the holder 14for the object to be processed within the processing vessel 4. The arm44 is then contracted, the gate valve G1 is closed, and the interior ofthe processing vessel 4 is sealed.

The interior of the processing vessel 4 is evacuated to a predeterminedprocessing pressure and also a processing gas is supplied in a showerfrom the gas supply head 28 thereinto, to maintain this processingpressure. Simultaneously therewith, power is supplied to the resistanceheaters 16 and 26 accommodated within the lower and upper heating meansvessels 6 and 8, or the power supplied thereto is increased, so that thewafer W mounted on the holder 14 is heated from both sides and ismaintained at the processing temperature, and a predetermined process isperformed thereon. In this case, the upper and lower resistance heaters26 and 16 control the supply of power to each zone individually, in sucha manner that the interior of the wafers surface is heated uniformly.

When chemical vapor deposition (CVD) is performed as the thermalprocessing by way of example, a mixture such as silane and hydrogen isused as the processing gas, argon is added as the carrier gas, theprocessing pressure is set on the order of 0.5 Torr, and the processingtemperature is set on the order of 1050° C.

In order to heat the wafer W in this case, the upper and lowerresistance heaters 26 and 16 are disposed above and below the wafer Wand also the heaters 26 and 16 are enclosed within the quartz heatingmeans vessels 8 and 6, respectively, so that the wafer can be heatedfrom both sides without causing contamination of the wafer. This ensuresthat the wafer is heated rapidly and also with a very uniform internaltemperature. As a specific result of making the thin portions 8A and 6Aof the heating means vessels 8 and 6 of this embodiment protrude in aconvex manner into the processing vessel 4, with the heaters 26 and 16disposed on inner surfaces thereof, the wafer surfaces and heatersurfaces are placed as close together as possible so that the distancestherebetween are extremely small, thus making it possible to furtherimprove the uniformity of temperature within the wafer surfaces, evenwith a larger wafer.

Since the thickness of the quartz thin portions 8A and 6A is set to beextremely thin at approximately 4 mm, thermal response is superiorbecause thermal losses from these portions are small and also theirthermal capacity is small, so that the temperature of the wafer W can becontrolled with good responsiveness.

By forming the gas supply head 28 to be flat and disposing it directlyunder the upper resistance heater 26 and also directly above the holder14 for the object to be processed, as shown in FIG. 2, the upperresistance heater 26 can be positioned in the vicinity of the uppersurface of the wafer W so that heating is performed at a high energy,moreover the processing gas can be supplied uniformly and directly overthe wafer W, and the formation of unwanted films on components such asthe processing vessel can be prevented.

Since each of the resistance heaters 26 and 16 is divided into aplurality of concentric circular zones, as shown in FIG. 3, and thesupply of power to each of these zones can be controlled individually,the wafer temperature can be controlled minutely.

Since the uniform-heating ring member 50 is provided at the peripheralportion of the wafer W so as to cover it, and thus the wafer W can alsobe heated by reflected radiant heat therefrom, not only can the surfaceuniformity of the wafer temperature be improved even further, but alsothe leakage of heat into the processing vessel is reduced so that thethermal efficiency can be improved by that much. The provision of theuniform-heating ring member 50 in this manner enables a hot-wallfunction thereof, it is therefore possible to ensure that the formationof unwanted films that adhere to the inner wall surfaces of theprocessing vessel in the prior art are made to adhere to the readilycleanable uniform-heating ring member 50 instead of the inner wallsurfaces of the vessel, making it easy to perform maintenance such ascleaning.

Since resistance heaters 16 and 26 of a high heat value are used in thiscase, the wafer can be heated to a high temperature of 1000° C. or more.Note that halogen lamps could be used instead of these heaters.

It could be considered that pressure changes within the processingvessel 4 could lead to pressure differences between that vessel and theheating means vessels 8 and 6 thereabove and therebelow, but since theconfiguration is such that the pressures within both the upper and lowerheating means vessels 8 and 6 are made to vary to follow the pressurewithin the processing vessel 4, so there is not damage to thepartitioning walls between these vessels. This will now be describedwith reference to FIG. 5.

As previously mentioned, fixed needle valves 62 and 70 are provided inthe branch pipelines 60 and 68 of the gas supply system 56 and gasexhaust system 64, respectively, with their configuration being suchthat the degree of opening thereof varies automatically with thepressure difference between the upstream and downstream sides thereof.

The description first concerns the state during evacuation wherein, ingeneral, if two vessels of different capacities are evacuatedindividually at the same flowrate, the pressure within thelarger-capacity vessel drops gently as shown by the curve L in FIG. 6A,but the pressure within the smaller-capacity vessel drops abruptly asshown by the curve S, causing a large pressure difference between thetwo vessels. However, if the exhaust-side fixed needle valves 70 areinserted into the branch pipelines 68 and if the evacuation is done at aconstant flowrate such as several liters per minute under the control ofthe mass-flow controller 72, as in the apparatus of this invention, theoperation of the fixed needle valves 70 ensures that the atmospherewithin the large-capacity processing vessel 4 is evacuated at a largerate with respect to the small quantity by which the atmosphere withinthe small-capacity upper and lower heating means vessels 8 and 6 isevacuated and, as a result, the pressure within the heating meansvessels 6 and 8 changes so as to follow the pressure within theprocessing vessel 4, as shown in FIG. 6B, and thus the evacuation occurswith the pressure differences between the processing vessel 4 and theheating means vessels 6 and 8 being maintained in a state in which theyare extremely small.

A similar state occurs when purging with N₂ to return the interior ofthe vessels to atmospheric pressure, such that, when N₂ is supplied, theN₂ is supplied while the pressure differences between the vessels arekept extremely small, as a result of the insertion of the fixed needlevalves 62 in the branch pipelines 60 of the gas supply system 56 shownin FIG. 5. Therefore, the pressure differences between the processingvessel 4 and the heating means vessels 6 and 8 become extremely small,such as on the order of 10 Torr. This means that the thin portions 6Aand 8A that separate the vessels need only be as thin as approximately 4mm, as previously mentioned, making it possible to suppress thermallosses and improve the thermal response. Note that the thick-plate lidportions 6B and 8B that are exposed to atmospheric pressure are formedto a thickness that enables them to resist atmospheric pressure.

Wafer temperature profiles were obtained by simulation for a case inwhich a wafer was subjected to single-surface heating and a case inwhich a wafer was subjected to two-surface heating, by disposing heatingmeans on both sides of the wafer in accordance with the presentinvention, with the results being as discussed below.

The wafer temperature profile obtained for the prior-art single-surfaceheating is shown in FIG. 7A and the wafer temperature profile obtainedfor two-surface heating in accordance with the present invention isshown in FIG. 7B. In each case, the heaters were divided into two zonesand the setting temperature was 1040° C.

With the single-surface heating shown in FIG. 7A, the temperaturedropped slightly closer to the peripheral portion of the wafer, so thata temperature difference on the order of 10° C. occurred between thatportion and the central portion thereof, the uniformity of temperaturewithin the surface was not very good, and moreover a rated power of 7 kWor more had to be applied to the heater in the outer zone during thistime. In contrast thereto, with the two-surface heating shown in FIG.7B, there was substantially no temperature difference between thecentral portion and peripheral portion of the wafer, and the uniformityof the temperature within the surfaces could be maintained at a highlevel. Moreover, the power used overall was slightly greater than in thesingle-surface heating case, but the power applied to the heater in eachzone was completely within the rated value.

The uniform-heating ring member 50 having the shutter portion 50A thatcan be raised and lowered to protect the gate valve G1 from heat isprovided in the above embodiment, as shown in FIG. 4, but instead it isalso possible to use a uniform-heating ring member 50 wherein the centerof one side surface thereof is provided with a slit-shaped aperture 50Bof a size that allows the wafer W to pass therethrough, as shown in FIG.8A. In that case, the configuration could be such that the component ismade to be rotatable, so that the uniform-heating ring member 50 can berotated through approximately 180 degrees after the wafer W has beenconveyed in or out, to protect the gate valve from heat.

Instead of the above configuration, a uniform-heating ring member 50could be used in which a concave cutout 50C of a size that allows thewafer W to pass therethrough is provided in a lower portion of one sidesurface thereof, as shown in FIG. 8B. In that case, the uniform-heatingring member 50 could be made rotatable or elevatable, so that theuniform-heating ring member 50 can be rotated through approximately 180degrees or moved downward after the wafer W has been conveyed in or out,to protect the gate valve from heat.

In addition, the above configuration was such that the gas supply head28 of a shower-head structure, the uniform-heating ring member 50, andthe holder 14 for the object to be processed were provided separatelyand independently, but instead a completely integral structure could beused in which the gas ejection holes are formed as a gas exhaust head 76of a configuration similar to that of the shower-head structure, asshown in FIGS. 9 to 11. In other words, a gas supply head 28' of ashower-head structure is linked to a uniform-heating ring member 50' ofthe configuration shown in FIG. 8A, and a holder 14' for the object tobe processed, which has three claw portions 14A attached thereto,protrudes towards the center from side wall surfaces of thisuniform-heating ring member 50'. The gas exhaust head 76 has ashower-head structure similar to that of the gas supply head 28 shown inFIG. 2 which is provided with a large number of suction holes 78 forsucking in gases in the upper surface thereof, and a gas exit portthereof could be connected to the gas exhaust port 34. This makes itpossible to form it integrally of a material such as quartz.

The above configuration ensures that a processing gas supplied from thegas supply head 28 towards the wafer W therebelow flows in such a mannerthat it strikes this surface then is made to flow laterally outwards inthe radial direction by the inner surfaces of the uniform-heating ringmember 50', until it is sucked into the gas exhaust head 76 thereunder.Therefore, the processing gas flows in such a manner that it strikes thewafer surface efficiently without expanding outward as far as theperipheral portions of the interior of the processing vessel 4, and thususage efficiency of the processing gas can be increased.

In addition, when an unwanted film has formed on this integralstructure, the integral structure alone can be cleansed, so thatmaintenance work can be performed efficiently.

In the above embodiment, the fixed needle valves 62 and 70 are providedin the gas supply system 56 and gas exhaust system 64, as shown in FIG.5, to control the pressure differences between the vessels, but thepresent invention is not limited thereto and a configuration such asthat shown in FIG. 12 could equally well be used. In other words,flowrate control valves 80A, 80B, 82A, and 82B with a degree of openingthat can be freely controlled are provided within the branch pipelines60 and 68 of the gas supply system 56 and gas exhaust system 64, insteadof needle valves in the branch pipelines 60 and 68 connected to theheating means vessels 6 and 8, but not such valves are provided in thebranch pipeline 60 connected to the processing vessel 4. In addition, afirst pressure difference measurement portion 84 is provided fordetecting a pressure difference between the processing vessel 4 and theinterior of the lower heating means vessel 6 therebelow, and a firstvalve opening control portion 86 controls the flowrate control valves80B and 82B on the supply side or exhaust side of the lower heatingmeans vessel 6 on the basis of the thus detected pressure difference.

Similarly, a second pressure difference measurement portion 88 isprovided for detecting a pressure difference between the processingvessel 4 and the interior of the upper heating means vessel 8thereabove, and a second valve opening control portion 90 controls theflowrate control valves 80A and 82A on the supply side or exhaust sideof the upper heating means vessel 8 on the basis of the thus detectedpressure difference.

This configuration ensures that the degrees of opening of the flowratecontrol valves 82A and 82B on the exhaust side are controlled during theevacuation process in such a manner that the detected values of thepressure difference measurement portions 84 and 86 are maintained withinthe pressure-resistant range of the thin portions 6A and 8A, such aswithin ±10 Torr. Similarly, the degrees of opening of the flowratecontrol valves 80A and 80B on the supply side are controlled during thepurging with N₂ to return the interior of the processing vessel 4 toatmospheric pressure, in such a manner that the detected values aremaintained within ±10 Torr. Therefore, an operative effect similar tothat of the configuration of FIG. 5 can be obtained in this embodimentas well.

Note that this embodiment was described as relating to the performanceof film formation by CVD as the thermal processing, by way of example,but it is not limited thereto and can of course be applied to otherforms of thermal processing such as oxidation, diffusion, or annealing.

In this case, the gate valve G1 is provided on only one side of theprocessing vessel 4 and the wafer is conveyed in and out therethrough,but another gate valve could be provided at a position opposite theretoso that the entrance port and exit port for the wafer are separate. Insuch a case, two of the shutter portions 50A or the like are providedfor the uniform-heating ring member 50, in correspondence thereto.

Furthermore, the object to be processed is not limited to asemiconductor wafer W; it could equally well be a glass substrate or anLCD substrate.

The thermal processing apparatus of the above described embodiment makesit possible to achieve the superlative operational effects describedbelow.

Since heating means is disposed on both sides of the object to beprocessed, to enable two-surface heating, the uniformity of temperaturewithin the surfaces thereof can be greatly improved, even when the sizeof the object to be processed is increased.

In addition, by accommodating each heating means in a heating meansvessel and allowing the pressure therein to vary to follow pressurechanges within the processing vessel, to keep pressure differencesbetween the vessels small, the partitioning walls that separate thevessels can be made thin so that, not only can the thermal efficiency beincreased by that amount and thus the uniformity of the surfacetemperature of the wafer can be improved, but also the thermal responsethereof can be made better.

Furthermore, covering the side portion of the object to be processed bythe uniform-heating ring member ensures that the amount of heatradiating to the exterior can be reduced, increasing the thermalefficiency, and also the uniformity of the surface temperature can beimproved by that amount. This uniform-heating ring member also makes itpossible to form a local hot-wall configuration so that unwanted filmscan be prevented from attaching to the side walls of the processingvessel, which also facilitates maintenance.

Integrating the gas supply head, the uniform-heating ring member, theholder for the object to be processed, and the gas exhaust head into asingle structure reduces the amount of processing gas leaking into theside portions, which not only makes it possible to improve the usageefficiency of the processing gas, it also facilitates maintenancefurther.

A second embodiment of the thermal processing apparatus in accordancewith this invention will now be described with reference to FIG. 13. Asshown in this figure, a thermal processing apparatus 122 is mainlyconfigured of a cylindrical processing vessel 136 formed of highly-purequartz; an upwardly convex inserted base portion 138 of highly-purequartz which is inserted into an aperture in a base portion of theprocessing vessel 136 to seal the interior of the processing vessel;resistance heating means 150A and 150B provided on a ceiling portionside and the inserted base portion 138 side of the processing vessel136, respectively; a holder 140 for holding a wafer W that is the objectto be processed; a gas supply head 141 that introduces a processing gasinto the processing vessel; and a position adjustment means foradjusting the heightwise position of the holder 140.

The processing vessel 136 is configured of a ceiling portion 136A thatcovers an upper portion thereof; an annular center vessel portion 136Bconnected thereto with a sealing member 144 such as an O-ringtherebetween; and a cylindrical lower vessel portion 136C connectedthereto with a sealing member 146 such as an O-ring therebetween. A gasexhaust port 148 connected to a vacuum exhaust system (not shown in thefigure) is provided in a side wall of the lower vessel portion 136C sothat the interior thereof can be evacuated.

The ceiling portion 136A is formed of transparent quartz through whichheat waves can pass, and it is also formed to be curved in a dome shapeso as to enable resistance to atmospheric pressure when the interior ofthe vessel is in a vacuum state, so that it can exhibit a predeterminedstrength even when the thickness thereof is small. The gas supply head141 is provided below this ceiling portion 136A in such a manner as toface the holder 140 for the object to be processed. The entire gassupply head 141 is formed of a material that enables the transmission ofheat waves, such as highly-pure transparent quartz. This gas supply head141 is formed in such a manner that the vertical section thereof has asemi-elliptical shape, a large number of gas ejection holes 152 areformed in a lower flat surface thereof, facing into the processingchamber, and also a gas introduction pipeline 154 extends upwards froman upper edge thereof and passes through a hole 156 provided in theceiling portion 136A, with a sealing member 158 such as an O-ringtherebetween to maintain the airtightness thereof.

A gas inlet port 160 is provided in the gas introduction pipeline 154,in such a manner that a predetermined processing gas can be introducedthereby. This gas introduction pipeline 154 has a double-walledstructure that accommodates a co-axial temperature measurement tube 162therein, a lower end of the gas introduction pipeline 154 passes throughthe gas supply head 141 and opens into the processing vessel, an upperend thereof is sealed by transparent quartz in an airtight manner, and aradiation thermometer 164 for measuring the surface temperature of thewafer is disposed in this upper end. The temperature measurement tube162 is provided in a direction that is substantially perpendicular tothe surface of the wafer W and is configured in such a manner thatradiant light from the wafer W can be detected directly by the radiationthermometer 164.

The resistance heating means 150A that is disposed on the ceilingportion 136A side is provided in such a manner as to cover the entiresurface of this ceiling portion 136A and is configured to supply thermalenergy from above the wafer W. An outer side of this resistance heatingmeans 150A is covered by a dome-shaped insulating member 166 formed of amaterial such as alumina. An upper surface of this insulating member 166could be configured to reflect heat waves downward by forming a film 161of a metal such as aluminum thereof by a method such as vapordeposition.

The resistance heating means 150A and the resistance heating means 150Bon the inserted base portion 138 side are formed of a resistance heatingwires that enable a high thermal load per unit area, of a material suchas molybdenum disilicide.

The ceiling portion 136A is formed of transparent quartz because of thenecessity of allowing heat waves to pass therethrough, but the centervessel portion 136B and lower vessel portion 136C that do notnecessitate the passage of heat waves therethrough are formed of, forexample, an opalescent non-transparent quartz wherein air bubbles arecomprised, so that the components themselves are formed aslight-blocking members.

The quartz inserted base portion 138 consists of a hollow convexinserted portion 138A of a diameter such that it is set to be somewhatsmaller than the inner diameter of the lower vessel portion 136C, withan outer diameter set so as to ensure the formation of a downwardexhaust passageway 166 of a predetermined width, and aring-flange-shaped base plate 138B provided in a lower end thereof andforming an airtight seal with a lower aperture of this convex insertedportion 138A with a sealing member 168 such as an O-ring therebetween.The lower end of the convex inserted portion 138A is open and anoptically transmissive plate 170 at an upper edge thereof is positioneddirectly below the holder 140 for the object to be processed and isformed to be curved in a downward concave shape; it exhibits apredetermined strength although it is thin enough to be of the samethickness of the ceiling portion 136A. The material of a leg portion ofthe convex inserted portion 138A is formed of, for example, anopalescent non-transparent quartz wherein air bubbles are comprised, sothat the component itself is formed as a light-blocking member.

A heater stand 172 is inserted from below into the convex insertedportion 138A that is opened at a lower end, an upper end thereof isformed in a concave curve and the resistance heating means 150B formedof a material such as molybdenum disilicide is mounted thereon, thusensuring that the wafer W is heated from below. In this case too, theresistance heating means 150B is formed of resistance heating wires of amaterial such as molybdenum disilicide that are wound in a circularconcentric manner, and it is divided into a number of concentric zones,such as three zones in the example shown in FIG. 15. Individual controlof each of these zones can be applied in a similar manner to theresistance heating means 150A of the ceiling portion 136A. This ensuresthat the energy aimed at the wafer W can be controlled in each zone.

The diameter L1 of this lower resistance heating means 150B is set to bewithin the range of 1.2 to 1.5 times the diameter L2 of the wafer W, sothat a sufficient quantity of energy can be aimed at the peripheralportions of the wafer W, where the quantity of radiant heat tends to begreater than at the center. A side portion heater 178 is provided on anupper side wall of the heater stand 172 for heating the leg portion ofthe convex inserted portion 138A, so that the leg portion is heatedthereby.

The heater stand 172 is formed of a material such as stainless steelwith an insulating member 179 of, for example, alumina interposedmidway, a cooling jacket 180 is provided at a lower end portion thereof,and the temperature of that portion is lowered to a safe temperature.

A gas introduction nozzle 155 for supplying an inert gas for gaspurging, such as N₂, is provided in the optically transmissive plate170, so that processing gas is prevented from circulating to the rearside of the wafer W by the introduction of N₂ therethrough.

The holder 140 on which the wafer W is mounted is also shown in FIG. 14;it is formed of highly-pure transparent quartz or SiC, it comprises anannular plate member of a diameter slightly greater than that of thewafer W, and a plurality of protrusions 182, such as three protrusions182, are formed equidistantly in the peripheral direction on uppersurface of an inner peripheral side thereof, to support the rear surfaceof the wafer W. In this case, the support positions of the wafer W arenot on the peripheral edge of the wafer, but they are arranged atpositions such that the support thereof is a certain distance closer tothe wafer center, to ensure that the amount of deformation of the waferitself during the thermal processing is controlled.

A plurality of leg portions 184, such as two leg portions 184, areformed on a rear surface side of the holder 140 arrayed in the diametricdirection of the holder 140, and these leg portions 184 are connected toposition adjustment rods 186 made of a material such as highly-purequartz.

These position adjustment rods 186 are formed as part of a heightwiseposition adjustment means 142, lower portions thereof are provided so asto pass in a freely movable manner vertically through holes formed inthe base plate 138B, and lower ends thereof are provided with gearmechanisms such as rack-and-pinion mechanisms that are driven by a motor188 in such a manner that the position adjustment rods 186 are forced tomove very slightly in the vertical direction to adjust the height of theholder 140. The portions of the position adjustment rods 186 that passthrough the base plate 138B are each provided with a freely expandablebellows 192 to permit the adjustment motion of the rods 186 whilemaintaining the airtightness of the vessel.

A connection port 194 connected to the load-lock chamber 42 is providedin one side portion of the center vessel portion 136B of the processingvessel 136, and a thermal screening box 191 is maintained in an airtightmanner in this connection port 194. Within this box 191 is provided athermal screening plate 198 that is moved vertically by an elevatormechanism 196 in such a manner as to shut off a passageway linking theconnection port 194 to the load-lock chamber 42, to restrain the amountof heat transferred to the gate valve G1 side. A bellows 195 is alsoprovided around a rod 193 of this elevator mechanism 196, to maintainthe airtightness of the vessel.

The operation of the thus configured second embodiment will now bedescribed.

First of all, an unprocessed semiconductor wafer W is brought into theload-lock chamber 42 through the gate valve G2 (see FIG. 1) by theconveyor arm 44, the interior thereof is evacuated to a predeterminedpressure, then the wafer is conveyed through the gate valve G1 into theprocessing vessel 136, which is maintained the previously set vacuumstate, and is transferred to the holder 140. This transfer of the waferW could be done by causing the motor 188 of the heightwise positionadjustment means 142 to operate in the normal direction, to move theholder 140 in the vertical direction, or the conveyor arm 44 itselfcould be made movable in the heightwise direction (Z direction) to causeit to move vertically.

This transfer causes the rear surface of the wafer W to be supported bythe protrusions 182 provided in the holder 140.

The interior of the processing vessel 136 has previously been heated toa certain degree, such as to 200 to 800° C., by the resistance heatingmeans 150A and 150B disposed at the top and bottom thereof, or it ismaintained fixed at the processing temperature, then further power isapplied after the wafer W has been conveyed thereinto to raise thetemperature to the processing temperature of, for example, approximately1200° C., or the processing temperature is held as is, until thetemperature within the wafer surface is uniform. Simultaneouslytherewith, the interior is held at a predetermined processing pressurewhile processing gases such as silane and O₂ are supplied into theprocessing vessel 136 from the gas supply head 141, and thermalprocessing such as film-formation processing is performed. Since amaterial that is capable of a high load density at a high current, suchas molybdenum disilicide, is used for the resistance heating means 150Aand 150B, the heating can be done to the predetermined temperaturerapidly.

In this case, a thin film is formed on surfaces such as the innersurfaces of the vessels, the surfaces of the gas supply head 141, andthe surfaces of the holder 140 for each processing of one wafer W or aplurality of wafers, even if it is only an extremely small amount, sothe thermal permittivity from the resistance heating means 150A and 150Bchanges very slightly, and it can happen that the quantity of heatsupplied to the wafer changes. In addition, it can happen that theprocessing gas supplied from the gas ejection holes 152 of the gassupply head 141 pools above the wafer surface. In such a case, theheightwise position adjustment means 142 is driven to raise or lower theposition adjustment rod 186 by a very small amount to raise or lower theholder 140 and thus adjust the height of the wafer, so that the spacingbetween the gas supply head 141 and the wafer W is adjusted to theoptimal position.

In this manner, the temperature of the wafer can be adjusted minutelyand also the processing gas can be prevented from pooling above thewafer, making it possible to increase the uniformity of film-formationover the wafer surface. This height-wise positional adjustment of thewafer makes it possible to adjust the height to suit the process, bothfor a procedure that implements the same thermal processing or for onethat implements different types of thermal processing, so that theoptimal temperature characteristics can always be achieved. Note that,if heightwise adjustment of the holder is to be done, not only could ifbe implemented by adjusting the spacing therefrom to the gas supplyhead, but it could be advantageous to implement it by enablingadjustment of the spacing therefrom to the resistance heating means, butit is also possible to vary the heightwise portion of the gas supplyhead portion by the heightwise adjustment means instead.

The temperature of the wafer W is measured by the radiation thermometer164 provided within the ceiling portion 136A, in which case, since lightgenerated upward from the surface of the wafer W is incident directly onthe radiation thermometer 164 through the hollow temperature measurementtube 162, there are no obstacles intercepting this light partway, andthus it is possible to detect the temperature of the wafer surface moreaccurately than by using a thermocouple. Note that the installationposition of the radiation thermometer 164 is not limited to thedirection perpendicular to the surface of the wafer W, provided it facesthe wafer surface directly, and it could be provided at an anglethereabove.

Since the diameter of the upper resistance heating means 150B is set tobe within a range that is 1.2 to 1.5 times the diameter of the wafer W,a large amount of energy can be aimed in a concentrated manner on theperipheral portions of the wafer, where the quantity of radiant heattends to be greater than at the center, and this makes it possible tosupplement the quantity of radiant heat and thus maintain a high degreeof uniformity of temperature within the wafer surface. Since the surfaceto which the resistance heating means 150B is attached is formed in aconcave shape directed towards the wafer, energy can be supplied moreefficiently towards the wafer W. In this case, each of the upper andlower resistance heating means 150A and 150B is configured in such amanner that it is divided into a plurality of concentric zones, such asthree zones, and temperature control is possible in each zone, so thatthe degree of uniformity of surface temperature in the wafer can beincreased further by controlling the thermal energy so that it increasestowards the outer zone, by way of example.

If the diameter of the resistance heating means 150B were less than 1.2times the diameter of the wafer W, it would become difficult to aimenough thermal energy at the peripheral portions to match the quantityof radiant heat therein, and thus the uniformity of surface temperaturewill deteriorate dramatically. If this diameter were greater than 1.5times, the diameter of the apparatus would become greater thannecessary, which is not preferable.

The configuration is such that the installation position of the gasexhaust port 148 is located higher than the horizontal level of thewafer W, so that the processing gas emitted from the gas supply head 141passes with virtually no pooling on the wafer surface, and is exhaustedfrom the gas exhaust port 148. In particular, this effect in combinationwith the previously described capability of adjusting the spacingbetween the wafer W and the gas supply head 141 makes it possible toreduce the phenomenon of gas pooling on the wafer surface to asubstantially undetectable level, enabling a further improvement in theuniformity of film formation over the surface.

Furthermore, since N₂ from the gas introduction nozzle 155 purges therear side of the holder 140, the processing gas does not intrude intothat area, thus making it possible to prevent the formation of films onsurfaces such as those of the holder 140, which makes it possible togreatly restrain deterioration in the thermal efficiency and thegeneration of particles.

Components such as the center vessel portion 136B, the lower vesselportion 136C, or the leg portion of the convex inserted portion 138A areformed of a non-transparent material so that light is excluded thereby,except for areas where the heat waves from the resistance heating means150A and 150B for heating the wafer W have to pass, so that thoseportions are not subjected to an unnecessary degree of heating, enablingan increase in thermal efficiency.

Since the ceiling portion 136A of the processing vessel 136 and theoptically transmissive plate 170 of the inserted base portion 138 areeach formed to be dome-shaped, sufficient strength with respect to theatmosphere can be ensured for those components, even when the thicknessthereof is thin.

Note that, although the second embodiment has been described above asbeing applied to film-formation as the thermal processing, by way ofexample, it is not limited thereto and can of course be applied to otherthermal processing such as oxidation or thermal diffusion. In addition,the object to be processed is not limited to a semiconductor wafer;another type of substrate such as an LCD substrate or glass substratecould also be used therein.

A third embodiment of the thermal processing apparatus of this inventionis shown in FIG. 16. This thermal processing apparatus is denotedoverall by reference number 2' and, since it has a structure that issimilar to that of the thermal treatment apparatus 2 that has alreadybeen described with reference to FIG. 2, except for certain portionsthereof, components that are the same as those of the first embodimentare given the same reference numbers and further description thereof isomitted, so that the description below concerns only the portions of thethird embodiment that differ from the first embodiment.

First of all, the uniform-heating ring member 50 and the elevatormechanism 52 and 53 provided in the first embodiment shown in FIG. 2 areomitted from this third embodiment.

A characteristic of the third embodiment is a holder 14' for the objectto be processed. This holder 14' for the object to be processed is madeof a thermal-resistant material such as quartz, as described above, ithas an annular holder base 254, and a central portion thereof is formedas a throughflow hole 260 to permit the vertical flow of gas. Thisthroughflow hole 260 makes it easy for heated gas to flow towards therear surface side of the wafer on the holder, so that the wafer can beheated efficiently and with a good uniformity of surface temperature.

A number of leg portions 256, such as three leg portions 256, are fixedto the holder base 254. Three support protrusions 258 are disposedsubstantially equidistantly in the peripheral direction on an uppersurface of this annular holder base 254 so as to protrude upward byapproximately 10 mm, and upper ends thereof are arranged to come intodirect contact with the peripheral edge of the rear surface of thesemiconductor wafer W, to support it. Note that the number of supportprotrusions 258 is not limited to three; this number could be increasedto six, by way of example, so that the load per support protrusion canbe reduced and also the amount by which the wafer distorts under its ownweight can be reduced.

In addition, an annular gas accumulation flange 262 is providedprojecting upward around the peripheral edge of the holder base 254, insuch a manner that heated gas accumulates on the rear surface side ofthe wafer to heat the wafer efficiently. In this case, the height of thegas accumulation flange 262 is on the order of a few mm shorter than theheight of the support protrusions 258, so that the conveyor arm 44 doesnot collide with the gas accumulation flange 262 during the conveying inor out of the wafer W. Note that this gas accumulation flange 262 couldalso be set to substantially the same height as the support protrusions258, with cutouts being formed therein only at portions where afork-shaped conveyor arm 44 pass.

The operation of the thus configured third embodiment will now bedescribed.

First of all, an unprocessed semiconductor wafer W from the load-lockchamber 42 is conveyed into the processing vessel 4 through the openedgate valve G1 and is received by the holder 14' for the object to beprocessed. In this case, the holder 14' has already been heated to theprocessing temperature or a lower temperature. The arm 44 is thencontracted, the gate valve G1 is closed, and the interior of theprocessing vessel 4 is sealed.

The interior of the processing vessel 4 is evacuated to a predeterminedprocessing pressure and also a processing gas is supplied in a showerfrom the gas supply head 28 thereinto, to maintain this processingpressure. Simultaneously therewith, power is supplied to the resistanceheaters 16 and 26 accommodated within the lower and upper heating meansvessels 6 and 8, or the power supplied thereto is increased, so that thewafer W mounted on the holder 14' is heated from both sides and ismaintained at the processing temperature, and a predetermined process isperformed thereon. In this case, the upper and lower resistance heaters26 and 16 control the supply of power to each zone individually, in sucha manner that the interior of the wafers surface is heated uniformly.

In particular, since the throughflow hole 260 is provided in the holderbase 254 of the holder 14' for the object to be processed in accordancewith this embodiment, heated internal environmental gases flow upwardsfrom below the holder 14' for the object to be processed and throughthis throughflow hole 260, as shown by arrows 264 (see FIG. 16), so thatthese heated gases come into contact with the rear surface of thesemiconductor wafer W, heat it, and flow outward horizontally. The gasaccumulation flange 262 provided on the peripheral edge portion of theholder base 254 temporarily impedes this flow of gases, so that thesegases flow outward through the space between the upper edge of the gasaccumulation flange 262 and the peripheral edge of the wafer, whilepooling therein.

The provision of the gas inlet port 160 in the gas introduction pipeline154 in this manner ensures that the heated gases rise and flow into therear surface side of the wafer, making it possible to increase theefficiency of wafer heating and further improve the uniformity of thesurface temperature thereof.

The gas accumulation flange 262 provided on the peripheral edge portionof the holder base 254 causes the heated gases pool temporarily on therear surface side of the wafer, making it possible to increase theefficiency of wafer heating and further improve the uniformity of thesurface temperature thereof, by that amount.

The support protrusions 258 of the holder base 254 of this embodimentare provided at three separate locations, but an annular supportprotrusion 268 could be provided instead, as shown in FIGS. 18 and 19.FIG. 18 is a sectional view through such a holder for the object to beprocessed and FIG. 19 is a partial cutaway perspective view thereof.

In this case, the annular support protrusion 268 shown in these figuresis formed to protrude upward in an annular manner around the peripheraldirection of the holder 14' and a plurality of gas removal holes 266 areprovided in a side wall thereof, of a rectangular form, for example.These gas removal holes 266 are formed at a predetermined spacing alongthe annular peripheral direction, but the size and number thereof arepreferably such as to increase the area of the passageways therethrough.This ensures that, after flowing from below and upward through thethroughflow hole 260 as shown by arrows 278 to strike the rear surfaceof the wafer and thus heat it, the heated gases flow outward through thegas removal holes 266. In this case too, this configuration not onlyincreases the wafer heating efficiency and the surface temperatureuniformity as described previously, the support protrusion 268 comesinto contact with the rear surface of the wafer, making it possible tosupport the weight thereof, and thus making it possible to restrain theoccurrence of slippage and crystal defects by that amount. This isparticularly effective for a 12-inch wafer wherein the size and also theself-weight of the wafer are greater.

In the above described embodiment, the throughflow hole 260 provided inthe holder base 254 was implemented as a large-diameter throughflowhole, but instead the holder base 254 could be formed as a circularplate and throughflow holes 270 could be provided therein by forming alarge number of small-diameter holes in the central portion thereof, asshown in FIG. 20.

In addition, when a wafer W at room temperature is conveyed into theprocessing vessel 4 by the conveyor arm 44 and placed on the holder 14'for the object to be processed in accordance with the above embodiment,the wafer W which is still at substantially room temperature is placedon the holder 14' for the object to be processed which has previouslybeen heated to a high temperature, so there is a danger that parts ofthe wafer W will be heated abruptly, causing slippage and crystaldefects to occur. To restrain these phenomena, after the wafer has beenconveyed in, that is, before it has been placed on the holder 14' forthe object to be processed, the wafer W could be conveyed into theprocessing vessel by the conveyor arm 44 then the wafer W could be madeto wait for a short while in a floating state until the wafer W has beenpre-heated to a predetermined temperature, as shown in FIG. 21. Thiswaiting time and the pre-heating temperature depend on the waferprocessing temperature, but if the processing temperature is 1000° C.,by way of example, the waiting time could be set on the order of 1 to 20seconds and the preheating of the wafer W could be to 600 to 700° C. Insuch a case, it is preferable that the distance L1 between the waitingwafer W and the support protrusions 258 of the holder 14' for the objectto be processed is set to be within a range on the order of 1.0 to 10mm, so that the pre-heating effect and the pre-heating time arebalanced.

In this manner, the utilization of a pre-heating method that makes thewafer float and wait within the processing vessel 4 ensures that thermalshock can be alleviated when the wafer W is placed upon the holder 14'for the object to be processed, thus making it possible to restrain theoccurrence of slippage and crystal defects.

In each of the above embodiments, the wafer W is placed directly on theholder 14' for the object to be processed, so that if, for example, thetemperature difference between the two objects is too great, there stillremains a danger that slippage and crystal defects will occur, even ifthe above described pre-heating has been performed. In order tosubstantially remove this danger completely, a supplementary supportstand could be provided that is conveyed in and out together with thewafer. The configuration of a thermal processing apparatus provided withsuch a supplementary support stand is shown in FIG. 22 and a perspectiveview of this supplementary support stand is shown in FIG. 23.

Since the thermal processing apparatus of FIG. 22 has exactly the samestructure as that of the thermal treatment apparatus 2 of FIG. 16,except that the configuration of the holder for the object to beprocessed is different and the supplementary support stand is provided,so components that are the same are given the same reference numbers andfurther description thereof is omitted. In other words, the provision ofthe holder 14' for the object to be processed on the three leg portions256 at the upper end of the support shaft 15 in the configuration ofFIG. 16 results in an integral structure, but in this case, a holder 272for the object to be processed is configured of the support shaft 15 andthe leg portions 256 provided at the upper end thereof. The holder 14'for the object to be processed of FIG. 16 is separated from the legportions 256 to form a supplementary support stand 274 in thisembodiment. Therefore, this supplementary support stand 274 has exactlythe same structure as the holder 14' for the object to be processed ofFIG. 16, except that this supplementary support stand 274 can beconveyed into and out of the processing vessel 4 together with the waferW, in a state in which the wafer W is placed thereon, so that thesupplementary support stand 274 can be placed on top of the holder 14'for the object to be processed. In FIG. 22, this supplementary supportstand 274 is shown in a state in which it is being conveyed outward intothe load-lock chamber 42.

The supplementary support stand 274 shown in FIG. 23 has an annularsupport stand base 276 made of a material that is resistant to heat,such as quartz, and a central portion thereof is formed as a throughflowhole 278 to permit the vertical flow of gas. This throughflow hole 278makes it easy for heated gas to flow towards the rear surface side ofthe wafer, so that the wafer can be heated efficiently and with a gooduniformity of surface temperature.

Three support protrusions 280 are disposed substantially equidistantlyin the peripheral direction on an upper surface of this annular supportstand base 276 so as to protrude upward by approximately 10 mm, andupper ends thereof are arranged to come into direct contact with theperipheral edge of the rear surface of the semiconductor wafer W, tosupport it. Note that the number of support protrusions 280 is notlimited to three; this number could be increased to six, by way ofexample, so that the load per support protrusion can be reduced and alsothe amount by which the wafer distorts under its own weight can bereduced.

In addition, an annular gas accumulation flange 282 is providedprojecting upward around the peripheral edge of the support stand base276, in such a manner that heated gas accumulates on the rear surfaceside of the wafer to heat the wafer efficiently. In this case, theheight of the gas accumulation flange 282 is on the order of a few mmshorter than the height of the support protrusions 280, so that theconveyor arm 44 does not collide with the gas accumulation flange 282when the wafer W is being separated from the supplementary support stand274. Note that this gas accumulation flange 282 could also be set tosubstantially the same height as the support protrusions 280, withcutouts being formed therein only at portions where a fork-shapedconveyor arm 44 pass.

Two supplementary support stand receptacles 284 are disposed within theload-lock chamber 42 for holding the supplementary support stand 274,with the configuration being such that they are used alternately. Notethat the number of supplementary support stand receptacles 284 is notlimited thereto, so that one or three or more could be provided, andthese supplementary support stand receptacles 284 are of course providedat locations which do not impede the conveyor arm 44.

If the description now turns to the flow of thermal processing when thissupplementary support stand 274 is used, an empty supplementary supportstand 274 has been placed on one of the supplementary support standreceptacles 284 in the load-lock chamber 42, then an unprocessed wafer Wis extracted from a cassette chamber (not shown in the figure) by theconveyor arm 44 and is moved onto the supplementary support stand 274.

The conveyor arm 44 is then contracted and extended to insert it underthe supplementary support stand 274 and hold the supplementary supportstand 274 together with the wafer W, then convey the supplementarysupport stand 274 together with the wafer W into the processing vessel 4through the opened gate valve G1. The supplementary support stand 274together with the wafer W is placed upon the holder 272 for the objectto be processed within the processing vessel 4, to complete the movementof the wafer W.

A predetermined thermal process is subsequently performed as describedpreviously, and, at the completion thereof, the above operation isreversed to convey the wafer W out. In other words, the conveyor arm 44is inserted below the supplementary support stand 274 to pick it uptogether with the wafer W, then the supplementary support stand 274 withthe wafer is moved into the load-lock chamber 42 by the contraction ofthe conveyor arm 44, and is placed on the supplementary support standreceptacle 284.

The wafer W is cooled to a certain extent by leaving it in this statefor a predetermined time. During this cooling, another supplementarysupport stand 274 could be used to convey an unprocessed wafer W intothe processing vessel 4 in the same manner as described previously.

When this cooling has been completed to a predetermined temperature, theconveyor arm 44 could be extended and contracted to pick up only thewafer W and convey it out towards a cassette chamber (not shown in thefigure), leaving the supplementary support stand 274 on thesupplementary support stand receptacle 284.

The use of the supplementary support stand 274 in this manner ensuresthat the conveyor arm 44 at room temperature does not come into directcontact with the wafer W which is at a high temperature directly afterbeing processed, so there is no abrupt cooling locally on the wafer Wand it is thus possible to prevent the occurrence of slippage andcrystal defects, substantially reliably. In addition, the supplementarysupport stand 274 is formed in a similar manner to the holder 14' shownin FIG. 16, so that heated gases can flow over the rear surface of thewafer, which also helps improve the heating efficiency and theuniformity of surface temperature of the wafer, as described previously.In this case, the above configuration of the holder 272 andsupplementary support stand 274 was merely given as an example; it is ofcourse not limited thereto. For example, the configuration could be suchthat the holder 14' shown in FIG. 16 is superimposed on thesupplementary support stand 274 so that thermal processing is performedwith a two-stage structure.

The support protrusions 280 of the support stand base 276 of the aboveembodiment are provided at three separate locations, but an annularsupport protrusion 286 could be provided instead, as shown in FIGS. 24and 25. FIG. 24 is a cross-sectional view through such a supplementarysupport stand and FIG. 25 is a partial cutaway perspective view thereof.

In this case, the support protrusion 286 shown in these figures isformed to protrude upward in an annular manner around the peripheraldirection of the supplementary support stand 274 and a plurality of gasremoval holes 288 are provided in a side wall thereof, of a rectangularform, for example. These gas removal holes 288 are formed at apredetermined spacing along the annular peripheral direction, but thesize and number thereof are preferably such as to increase the area ofthe passageways therethrough. This ensures that, after flowing frombelow and upward through the throughflow hole 278 as shown by arrows 290to strike the rear surface of the wafer and thus heat it, the heatedgases flow outward through the gas removal holes 288. In this case too,this configuration not only increases the wafer heating efficiency andthe surface temperature uniformity as described previously, the supportprotrusion 286 comes into contact with the rear surface of the wafer,making it possible to support the weight thereof, and thus making itpossible to restrain the occurrence of slippage and crystal defects bythat amount. This is particularly effective for a 12-inch wafer whereinthe size and also the self-weight of the wafer are greater. Referencenumber 282 denotes an annular gas accumulation flange.

In the above described embodiment, the throughflow hole 278 provided inthe support stand base 276 was implemented as a large-diameterthroughflow hole, but instead support stand base 276 could be formed asa circular plate and throughflow holes 292 could be provided therein byforming a large number of small-diameter holes in the central portionthereof, as shown in FIG. 26.

Furthermore, in each of the above described embodiments, the descriptionconcerned a configuration in which the load-lock chamber 42 and theprocessing vessel 4 were connected directly by a gate valve G1, by wayof example, but the configuration is not limited thereto and apre-heating chamber 296 could be provided between the processing vessel4 and the load-lock chamber 42, separated therefrom by freely openablegate valves G3 and G4. A heating stand 300 with an internal heater 298is provided within this pre-heating chamber 296, and either a wafer Walone or a wafer W placed upon the supplementary support stand 274 couldbe pre-heated therein. Not only does this make the thermal shock withrespect to the wafer even smaller and also further reduce the occurrenceof slippage and crystal defects, the amount of pre-heating also makes itpossible to improve the throughput of the thermal processing. Note thatthe stroke of the conveyor arm 44 used in this case is of course set tolong enough for the length of the pre-heating chamber 296.

INDUSTRIAL APPLICABILITY

Other than semiconductor wafers, the present invention can be used forthe thermal processing of glass substrates, LCD substrates, or the like.Other than film-formation, this thermal processing includes oxidation,diffusion, and annealing.

What is claimed is:
 1. A single-wafer type of thermal processingapparatus provided with a processing vessel and a holder for an objectto be processed, which is provided within said processing vessel to holdan object to be processed, wherein said thermal processing apparatuscomprises:a lower heating means provided within said processing vesseland below said holder for an object to be processed, for heating saidobject; a lower heating means vessel for entirely enclosing said lowerheating means in a sealed state with respect to said processing vessel;an upper heating means provided within said processing vessel and abovesaid holder, for heating said object; an upper heating means vessel forentirely enclosing said upper heating means in a sealed state withrespect to said processing vessel; a processing gas supply means forsupplying a processing gas to an area between said holder and said upperheating means; means for maintaining said processing vessel and saidlower and upper heating means vessels at predetermined pressures; and agas supply system connected to said processing vessel and said twoheating means vessels, for supplying a gas while maintaining thepressure within said three vessels to within a predetermined pressurerange.
 2. The thermal processing apparatus as defined in claim 1,further comprising a gas exhaust system connected to said processingvessel and said two heating means vessels, for exhausting the internalatmosphere while maintaining the pressure within said three vessels towithin a predetermined pressure range.
 3. The thermal processingapparatus as defined in claim 2, wherein each of said gas supply systemand said gas exhaust system comprises a common gas passageway connectedin common to said three vessels, passageways linking said common gaspassageway to said vessels, and a differential pressure drive valveinterposed within said passageways.
 4. The thermal processing apparatusas defined in claim 2, wherein each of said gas supply system and saidgas exhaust system comprises a common gas passageway connected in commonto said three vessels, passageways linking said common gas passageway tosaid vessels, a first flowrate control valve provided in a passagewayconnecting said common gas passageway to said lower heating meansvessel, a second flowrate control valve provided in a passagewayconnecting said common gas passageway to said upper heating meansvessel, means for controlling the degree of opening of said firstflowrate control valve in accordance with a difference between thepressure within said processing vessel and said lower heating meansvessel, and means for controlling the degree of opening of said secondflowrate control valve in accordance with a difference between thepressure within said processing vessel and said upper heating meansvessel.
 5. A single-wafer type thermal processing apparatus providedwith a processing vessel and a holder for an object to be processed,which is provided within said processing vessel to hold an object to beprocessed, wherein said thermal processing apparatus comprises:a lowerheating means provided within said processing vessel and below saidholder for an object to be processed, for heating said object; a lowerheating means vessel for accommodating said lower heating means in asealed state with respect to said processing vessel; an upper heatingmeans provided within said processing vessel and above said holder, forheating said object; an upper heating means vessel for accommodatingsaid upper heating means in a sealed state with respect to saidprocessing vessel; a processing gas supply means for supplying aprocessing gas to an area between said holder and said upper heatingmeans; means for maintaining said processing vessel and said lower andupper heating means vessels at predetermined pressures; and acylindrical uniform-heating ring member positioned on a peripheral edgeof said holder to cover a side portion of said object held on saidholder, wherein said uniform-heating ring member is capable of changingposition vertically.
 6. The thermal processing apparatus as defined inclaim 1, wherein said lower and upper heating means are electricalresistance heaters.
 7. The thermal processing apparatus as defined inclaim 1, wherein said holder is provided in a manner capable of verticalpositional adjustment.
 8. The thermal processing apparatus as defined inclaim 1, wherein said processing gas supply portion has flattened shapein the horizontal direction, with a large number of processing gasejection holes in a lower surface thereof.
 9. The thermal processingapparatus as defined in claim 1, further comprising a gas exhaust portat a position lower than that of said holder, for evacuating theatmosphere within said processing vessel.
 10. The thermal processingapparatus as defined in claim 1, wherein each of said lower and upperheating means is divided into a plurality of concentric zones, such thattemperature control can be provided for each of said zones.
 11. Thethermal processing apparatus as defined in claim 1, wherein each of saidlower and upper heating means has a diameter that is between 1.2 and 1.5times the diameter of said object to be processed.
 12. The thermalprocessing apparatus as defined in claim 1, wherein said holdercomprises a holder base; a support protrusion protruding upwardtherefrom, for supporting a peripheral edge portion of a rear surface ofsaid object to be processed; and a gas throughflow hole provided in saidholder base, for permitting gases to flow in the vertical direction. 13.The thermal processing apparatus as defined in claim 12, Wherein saidsupport protrusion is formed in an annular shape and is also providedwith gas removal holes.
 14. The thermal processing apparatus as definedin claim 1, further comprising a supplementary support stand which iscapable of being mounted on said holder and which also receives saidobject to be processed directly, wherein said supplementary supportstand is capable of being conveyed into said processing vessel and outof said processing vessel with said object to be processed receivedthereon.